1. Field of the Invention
This invention concerns new polymers and a method for reducing haze formation in a hydrodewaxed mineral oil base stock using same. More particularly, it relates to polymer made by reacting a polyanhydride resin with an alcohol and to a method of lowering the cloud point of the base stock by treating same the polymer.
2. Discussion of the Prior Art
Many hydrodewaxed base oils have relatively high cloud points. While other properties are excellent and the cloud point appears to have no deleterious effect on the performance of formulated oils, nevertheless there are specification tests for many oils that require that there be no overnight cloud formation in the base oil at a given temperature, often 30.degree. F. to 40.degree. F.
The high cloud point (or overnight cloud point, ONC) is common to many hydrodewaxed oils. Much processing work, such as selective removal of the haze components and use of crystallization inhibitors, has been done with limited success. Generally, solutions to the haze formation are uneconomic or impractical because the solutions introduce other problems such as lower viscosity index, poor storage stability, dark color, water emulsification tendency, poorer oxidation response, and the like.
No prior art is known that teaches or suggests that the herein disclosed useful results can be obtained by reacting a maleic anhydride-olefin copolymer with an alcohol and adding same to a hydrodewaxed base stock. The closest prior art known is U.S. Pat. No. 4,194,985, which teaches compounds prepared by the free radical polymerization of an ethylenically unsaturated monomer (which can be an alpha olefin) in the presence of an oil soluble dispersant (e.g., product of reaction between a carboxylic acid containing, at least 34 aliphatic carbon atoms with, inter alia, an alcohol). Table 1, which teaches typical dispersants, discloses the reaction product between, e.g., methyl or oleyl alcohol and polyisobutenylsuccinic anhydride. The polyisobutenylsuccinic compound is not polymeric, as is applicant's compounds, and the reaction carried out by patentee in the presence of the free radical initiator does not produce such polymer. If indeed any reaction at all takes place, it is merely a grafting of the unsaturated reactant to the aliphatic portion.